09-26-2008, 12:50 PM
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Why did you settle on crushed coral? Crushed coral will increase the pH and hardness of your water substantially, so in freshwater tanks it's usually only used with African Rift Lake cichlids that prefer those conditions. Most tropical fish (tetras, barbs, loaches, dwarf cichlids, etc etc) generally prefer softer water and a lower pH.
Also, if you're looking to get some sort of eel, they'd really prefer a soft sand substrate rather than that jagged coral. Keep in mind that you're somewhat limited when it comes to eels, especially in a tank that size.
Why the powerhead? Generally powerheads used just for water movement purposes are reserved for saltwater tanks. For freshwater, you don't need to add water movement unless you're keeping river fish or something. Usually the filtration you'll have in the tank provides enough water movement to keep the fish happy.